US20030223164A1 - Semiconductor apparatus and protection circuit - Google Patents
Semiconductor apparatus and protection circuit Download PDFInfo
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- US20030223164A1 US20030223164A1 US10/400,410 US40041003A US2003223164A1 US 20030223164 A1 US20030223164 A1 US 20030223164A1 US 40041003 A US40041003 A US 40041003A US 2003223164 A1 US2003223164 A1 US 2003223164A1
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- diffusion region
- pad
- protection circuit
- semiconductor substrate
- power supply
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier
- H01L27/0203—Particular design considerations for integrated circuits
- H01L27/0248—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection
- H01L27/0251—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices
- H01L27/0266—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices using field effect transistors as protective elements
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
- H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L24/02—Bonding areas ; Manufacturing methods related thereto
- H01L24/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
- H01L24/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/02—Bonding areas; Manufacturing methods related thereto
- H01L2224/0212—Auxiliary members for bonding areas, e.g. spacers
- H01L2224/02122—Auxiliary members for bonding areas, e.g. spacers being formed on the semiconductor or solid-state body
- H01L2224/02163—Auxiliary members for bonding areas, e.g. spacers being formed on the semiconductor or solid-state body on the bonding area
- H01L2224/02165—Reinforcing structures
- H01L2224/02166—Collar structures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/02—Bonding areas; Manufacturing methods related thereto
- H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
- H01L2224/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
- H01L2224/05001—Internal layers
- H01L2224/05075—Plural internal layers
- H01L2224/0508—Plural internal layers being stacked
- H01L2224/05085—Plural internal layers being stacked with additional elements, e.g. vias arrays, interposed between the stacked layers
- H01L2224/05089—Disposition of the additional element
- H01L2224/05093—Disposition of the additional element of a plurality of vias
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/02—Bonding areas; Manufacturing methods related thereto
- H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
- H01L2224/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
- H01L2224/0554—External layer
- H01L2224/0555—Shape
- H01L2224/05552—Shape in top view
- H01L2224/05554—Shape in top view being square
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/02—Bonding areas; Manufacturing methods related thereto
- H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
- H01L2224/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
- H01L2224/0554—External layer
- H01L2224/0555—Shape
- H01L2224/05556—Shape in side view
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/10—Details of semiconductor or other solid state devices to be connected
- H01L2924/11—Device type
- H01L2924/13—Discrete devices, e.g. 3 terminal devices
- H01L2924/1304—Transistor
- H01L2924/1306—Field-effect transistor [FET]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/10—Details of semiconductor or other solid state devices to be connected
- H01L2924/11—Device type
- H01L2924/13—Discrete devices, e.g. 3 terminal devices
- H01L2924/1304—Transistor
- H01L2924/1306—Field-effect transistor [FET]
- H01L2924/13091—Metal-Oxide-Semiconductor Field-Effect Transistor [MOSFET]
Definitions
- This invention generally relates to a protection circuit for preventing destruction of an internal circuit possibly caused by excessive voltage input from a pad, and to a semiconductor apparatus employing the protection circuit.
- FIGS. 10A and 10B entirely and partially illustrate GND (ground) and power supply pads mounted on a conventional semiconductor apparatus 46 formed from a P-type semiconductor substrate 3 .
- an inner core region 5 is formed at a central portion of the semiconductor apparatus 46 .
- An inner circuit formed from a plurality of semiconductor elements is located in the inner core region 5 .
- a plurality of pad areas 7 is also formed in an outer region 15 of the semiconductor apparatus 46 .
- An I/O cell 47 is provided per pad area 7 on the semiconductor substrate 3 between the inner core region 5 and pad area 7 .
- an inner core region use Vcc line 11 a and an inner core region use GND (ground) line 11 b each formed from a metal wiring layer, between the inner core region 5 and I/O cell 47 .
- Lines 11 a and 11 b continuously circumscribe the inner core region 5 .
- an I/O cell use Vcc line 49 a and an I/O cell use GND line 49 b each formed from a metal wiring layer, are provided.
- the inner core region use Vcc line 11 a and I/O cell use Vcc line 49 a are electrically connected to a metal wiring layer 51 a which is electrically connected to an electric power supply use pad area 7 a through via holes 11 c and 49 c .
- the inner core region use GND line 11 b and I/O cell use GND line 49 b are electrically connected to the metal wiring layer 51 b which is electrically connected to a GND use pad area 7 b through via holes 11 d and 49 d .
- the inner core region use Vcc line 11 a is electrically connected to a metal wiring layer 53 a extending over in the side of inner core region 5 through a via hole 11 e .
- the inner core region use GND line 11 b is electrically connected to a metal wiring layer 53 b extending over to the side of inner core region 5 through a via hole 11 f.
- FIG. 11 illustrates an exemplary configuration of a conventional pad area 7 and I/O cell 47 .
- FIG. 12 illustrates an equivalent circuit thereof.
- Each I/O cell 47 is configured from a protection circuit and input buffer 17 .
- the protection circuit is configured from a P-channel type MOSFET (Metal Oxide Silicon Field Effect Transistor) Tr 5 (herein after referred to as a MOS transistor Tr 5 ), a N-channel type MOS transistor Tr 6 , and a resister R (not shown).
- MOSFET Metal Oxide Silicon Field Effect Transistor
- the MOSFET transistor Tr 5 is formed in a P channel region of a N-well formed on the P-type semiconductor substrate.
- a gate electrode is configured from a polysilicon electrode 55 .
- An area required for forming the MOS transistor Tr 5 is approximately 1800 ⁇ m.
- the MOS transistor Tr 6 is formed in an N-channel region of a P-type semiconductor substrate. Both source and drain of the MOS transistor Tr 6 are configured from a N-type impurity diffusion layer (N-type impurity) formed on the P-type semiconductor substrate.
- a gate electrode is configured from a polysilicon electrode 57 . An area required for forming the MOS transistor Tr 6 is approximately 1000 ⁇ m.
- both the poly-silicon gate electrode 55 and a source of the MOS transistor Tr 5 are connected to power supply “Vcc”. Respective drains of the MOS transistors Tr 5 and Tr 6 are connected to each other, and further connected to the pad area 7 . Both the poly-silicon gate electrode 57 and source of the MOS transistor Tr 6 are connected to ground “GND”. One end of the resistance is connected to a connection point connecting drains of the MOS transistors Tr 5 and Tr 6 .
- the input buffer 17 is configured from an inverter circuit formed from P-channel type and N-channel type MOS transistors Tr 3 and Tr 4 .
- the MOS transistor Tr 3 is formed in the P-channel region of the N-well formed on the P-type semiconductor substrate. Both the source and drain of the MOS transistor Tr 3 are configured from P-type impurity diffusion layers formed in the N-well.
- a gate electrode is configured from a polysilicon electrode 59 .
- the MOS transistor Tr 4 is formed in an N-channel region of the P-type semiconductor substrate. Both the source and drain of the MOS transistor Tr 4 are configured from N-type impurity diffusion layers (N-type impurity) formed on a P-type semiconductor substrate.
- a gate electrode is configured from a polysilicon electrode 61 , as shown in FIG. 11.
- the source of the MOS transistor Tr 3 is connected to the power supply “Vcc”.
- the source of the MOS transistor Tr 4 is connected to ground (GND).
- Respective drains of the MOS transistors Tr 3 and Tr 4 are connected to each other, and are lead to the inner core region 5 .
- Respective polysilicon gates 59 and 61 of the MOS transistors Tr 3 and Tr 4 are connected to each other, and further connected to the other end of the resistance.
- a protection circuit for an I/O cell is typically provided.
- the inner core region is downsized, and accordingly, the I/O cell increases a rate of its occupation in a semiconductor apparatus.
- the I/O cell increases a rate of its occupation in a semiconductor apparatus.
- Japanese patent application Laid Open No. 2000-12778 discloses one example. Specifically, a protection circuit is formed on an N-type semiconductor substrate, having an NPN configuration. The protection circuit is formed from an N-implant diffusion layer, a P-type island region including a P-implant layer and P-diffusion layer, and a N-diffusion layer formed on the island region.
- an object of the present invention is to address such problems and provide a new protection circuit for use in a semiconductor apparatus.
- the protection circuit includes a first conductivity type semiconductor substrate, a second conductivity type first diffusion region formed on the semiconductor substrate, and a second conductivity type second diffusion region formed on the semiconductor substrate.
- the second diffusion region is distanced at a prescribed interval from the first diffusion region, and the first diffusion region is electrically connected to a pad for electrically connecting the inner circuit to an outside region.
- the second diffusion region is electrically connected to a power supply. At least a portion of said first and second diffusion regions is formed right under a pad area.
- the first and second diffusion regions are substantially entirely formed right under the pad area.
- the first and second diffusion regions are separated from each other by a field oxide coat formed on the surface of the semiconductor substrate. At least a portion of the field oxide coat is located right under the pad area.
- a second conductivity type third diffusion region is formed on the surface of the semiconductor substrate and located in an opposite side at a prescribed interval from the first diffusion region to the second diffusion region.
- the second diffusion region is electrically connected to a higher voltage of the power supply.
- the third diffusion region is electrically connected to a lower voltage of the power supply. At least a portion of the third diffusion region is formed right under the pad area.
- the third diffusion region is substantially entirely formed right under the pad area.
- the first and second diffusion regions, and the first and third diffusion regions are separated, respectively, from each other by a field oxide coat. At least a portion of the pad area is formed on the field oxide coat.
- the electrical connection is performed by at least one via hole formed right under the pad area.
- FIG. 1A is a chart when viewed from a section C-C illustrated in FIGS. 1B and 1C;
- FIG. 1B is a chart when viewed from a section A-A illustrated in FIG. 1A;
- FIG. 1C is a chart when viewed from a section B-B illustrated in FIG. 1A;
- FIG. 2A is a plan view illustrating one embodiment
- FIG. 2B is an enlarged view illustrating a portion framed by a circle (dotted circle) in FIG. 2A;
- FIG. 3 is a chart illustrating one example of an equivalent circuit of a pad area 7 and I/O cell 9 ;
- FIG. 4A is a cross-sectional view illustrating one example of an outer region of a Vcc use pad
- FIG. 4B is a cross-sectional view illustrating one example of an outer region of a GND use pad
- FIG. 5 is a cross-sectional view illustrating an exemplary protection circuit applied to a six-layer metal wiring structure
- FIG. 6A is a cross-sectional view illustrating one example of an outer region of a protection circuit employing a MOS transistor having a poly-silicon gate as a protection element;
- FIG. 6B is a chart when viewed from a section A-A of FIG. 6A;
- FIG. 6C is a chart when viewed from a section B-B of FIG. 6A;
- FIG. 7 is a chart illustrating one example of an equivalent circuit of a pad and I/O cell
- FIG. 8A is a chart illustrating another embodiment of a protection circuit employing a field transistor as a protection element, when viewed from a section CC of FIGS. 8B and 8C;
- FIG. 8B is a plan view when viewed from a section A-A of FIG. 8A;
- FIG. 8C is a chart when viewed from a section B-B of FIG. 8A;
- FIG. 9 is a chart illustrating another example of an equivalent circuit of an I/O cell
- FIG. 10A is a plan view entirely illustrating a conventional semiconductor apparatus
- FIG. 10B is an enlarged plan view partially illustrating GND and a pad
- FIG. 11 is a plan view illustrating an example of a pad area 7 and I/O cell 47 ;
- FIG. 12 is a chart illustrating an equivalent circuit of the conventional pad and I/O cell.
- FIG. 13 is a chart showing an example of a table showing surge impressed voltages and conditions of energy divergence factors.
- FIGS. 1A, 1B, 2 A and 2 B one embodiment of an outer region of a protection circuit of a semiconductor apparatus is illustrated.
- an inner core region 5 is formed at a central section of a semiconductor apparatus 1 formed from a P-type semiconductor substrate 3 .
- An inner circuit formed from a plurality of semiconductor elements is formed in the inner core region 5 .
- a plurality of pads is also formed in an outer region of the semiconductor apparatus 1 .
- an I/O cell 9 is arranged per a pad area 7 on the semiconductor substrate 3 , including a range for forming the pad area 7 .
- An inner core region use Vcc line 11 a and an inner core region use GND line 11 b are continuously formed between the inner core region 5 and I/O cell 9 almost surrounding the inner core region 5 .
- Such a Vcc represents a high potential of a power supply.
- the GND represents a lower potential of the power supply.
- the inner core region use Vcc line 11 a and I/O cell use Vcc line 13 a are configured by metal wirings arranged on a layer lower than the pad area 7 .
- the inner core region use Vcc line 11 a and I/O cell use Vcc line 13 a are electrically connected to a power supply use pad area 7 via a metal wiring layer (not shown) formed on a layer where the pad area 7 is formed.
- the inner core region use GND line 11 b and I/O cell use GND line 13 b are configured by metal wirings arranged on a layer lower than the pad area 7 .
- the inner core region use GND line 11 b and I/O cell use GND line 13 b are electrically connected to a GND use pad area 7 via the metal wiring layer (not shown) formed on the layer where the pad area 7 is formed.
- FIG. 3 illustrates one example of an equivalent circuit of a pad area 7 and I/O cell 9 .
- a protection circuit 15 and an input buffer 17 configure each I/O cell 9 .
- the protection circuit 15 is configured from an N-channel type field transistor Tr 1 , a N-channel type field transistor Tr 2 , and a resistance R formed from a diffusion layer. Even though the diffusion layer configures the resistance R, a resistance formed from a polysilicon coat and a metal lamina can be utilized therefor.
- the drain of the N-channel type field transistor Tr 1 is connected to the power supply Vcc.
- the source and drain of the field transistors Tr 1 and Tr 2 are connected to each other, and then connected to the pad area 7 .
- the gate electrodes of the field transistors Tr 1 and Tr 2 are connected to each other, and then connected to the pad area 7 .
- One end of the resistance R is connected to a connection point connecting the source of the field transistor Tr 1 to the drain of the field transistor Tr 2 .
- an inverter circuit formed from P-channel type and N-channel type MOS transistors Tr 3 and Tr 4 configures the input buffer 17 .
- the source of the MOS transistor Tr 3 is connected to the power source Vcc.
- the source of the MOS transistor Tr 4 is connected to GND.
- the drains of the MOS transistors Tr 3 and Tr 4 are connected to each other, and then lead to the inner core region 5 .
- the gate electrodes of the MOS transistors Tr 3 and Tr 4 are connected to each other, and then connected to the other end of the resistance R.
- the diffusion type resistance R is formed on a P-type semiconductor substrate 3 between the pad area 7 in an I/O cell 9 formation region and the inner core region use Vcc line 11 a.
- N-type impurity diffusion regions 19 a , 19 b , and 19 c are formed on a surface of a P-type semiconductor substrate (P-substrate).
- An oxide film 21 separates these N-type impurity diffusion regions 19 a , 19 b , and 19 c from each other.
- the N-type impurity diffusion region 19 a is distanced from the N-type impurity diffusion region 19 c .
- the N-type impurity diffusion region 19 b is formed in an opposite side and distanced from the N-type impurity diffusion region 19 c and the N-type impurity diffusion region 19 a .
- the N-type impurity diffusion region 19 a constitutes a second diffusion range forming the protection circuit of the semiconductor apparatus.
- the N-type impurity diffusion region 19 b serves as a third diffusion region.
- the N-type impurity diffusion region 19 c serves as a first diffusion region.
- the N-type impurity diffusion region 19 a corresponds to the drain of the field transistor Tr 1 of FIG. 3.
- the N-type impurity diffusion region 19 b corresponds to the source of the field transistor Tr 2 of FIG. 3.
- the N-type impurity diffusion region 19 c corresponds to the source of the field transistor Tr 1 and the drain of the field transistor Tr 2 of FIG. 3.
- An insulation coat 23 is formed on the surfaces of the N-type impurity diffusion regions 19 a , 19 b and 19 c .
- the lowest metal wiring layers 25 a , 25 b , and 25 c are separately formed from each other on field oxide coat 21 and insulation coat 23 .
- the lowest metal wiring layer 25 a is also electrically connected to the N-type impurity diffusion region 19 a through a via hole formed through the insulation coat 23 .
- the lowest metal wiring layer 25 b is electrically connected to the N-type impurity diffusion region 19 b through a via hole formed through the insulation coat 23 .
- the lowest metal wiring layer 25 c is electrically connected to the N-type impurity diffusion region 19 c through a via hole formed in the insulation coat 23 .
- the lowest metal wiring layer 25 c is formed on the field oxide coat 21 extending over from a portion between the N-type impurity diffusion regions 19 a and 19 c to that between the N-type impurity diffusion regions 19 b and 19 c .
- the metal wiring layer 25 c corresponds to the gate electrodes of the field transistors Tr 1 and Tr 2 of FIG. 3.
- An interlaminar insulation layer 27 is formed on the field oxide coat 21 , insulation coat 23 , and lowest metal wiring layers 25 a , 25 b , and 25 c . Further, an I/O cell use Vcc line 13 a , an I/O cell use GND line 13 b , and a metal wiring layer 13 c each formed from a metal wiring layer are formed on the layers. The I/O cell use Vcc line 13 a , and I/O cell use GND line 13 b are continuously formed extending over a region, where a plurality of pads are formed thereabove, as illustrated in FIG. 2B.
- FIG. 1A there are provided via holes through the interlaminar insulation layer 27 for electrically connecting the lowest metal wiring layers 25 a , 25 b , and 25 c to I/O cell use Vcc lines 13 a , 13 b , and 13 c , the lowest metal wiring layer 25 b to I/O cell use GND line 13 b , and the lowest metal wiring layer 25 c to metal wiring layer 13 c , respectively.
- an inter-laminar insulation layer 29 is formed on the inter-laminar insulation layer 27 , I/O cell use Vcc line 13 a , I/O cell use GND line 13 b , and metal wiring layer 13 c . Further, a pad area 7 , formed from a metal wiring layer, is formed on the layers.
- a passivation coat 31 is formed on the inter-laminar insulation layer 29 and pad area 7 . There is formed a pad opening section on a pad area 7 of the passivation coat 31 . A plurality of via holes are formed so as to electrically connect the metal wiring layer 13 c to the pad area 7 .
- any one of pads 7 on the semiconductor apparatus 1 is utilized as a Vcc use pad area 7 a .
- a plurality of via holes are formed through the inter-laminar insulation coat 29 right under a Vcc use pad area 7 a so as to electrically connect the Vcc use pad area 7 a to the I/O cell use Vcc line 13 a.
- any one of pads 7 on the semiconductor apparatus 1 beside the Vcc use pad area 7 a is utilized as a GND use pad area 7 b .
- a plurality of via holes are formed through the inter-laminar insulation coat 29 right under a GND use pad area 7 b so as to electrically connect the GND use pad area 7 b to the I/O cell use GND line 13 b.
- a surge-impressed voltage represents a voltage excessively impressed to a pad area 7 .
- HBM Human Body Model
- this embodiment employs the three layer metal wiring structure as illustrated in FIG. 1A.
- one, two, and more than four layer metal wiring structures can be employed in a semiconductor apparatus.
- both the power supply and GND lines are formed other than the range for the pad.
- each of the lowest metal layer wiring layers 25 a , 25 b and 25 c , I/O cell use Vcc line 13 a , I/O cell use GND line 13 b , metal wiring layer 13 c , and pad area 7 amount to almost 700 nm (nanometer), and that of the interlaminar insulation layers 27 and 29 almost 800 nm, respectively. Accordingly, a coat thickness from the surface of the field oxide film to that of the pad area 7 amounts to about 3700 nm in the three metal wiring structures.
- the design rule includes dimensions that are quarter or sub-quarter micron.
- the six-layer metal wiring structure that employs such a design rule may be employed in the semiconductor apparatus.
- FIG. 5 is a cross-sectional view illustrating an exemplary protection circuit employing the six layer metal wiring structure.
- the N-type impurity diffusion regions 19 a , 19 b and 19 c are separated by a field oxide film 2 and formed on the surface of the P-type semiconductor substrate 3 .
- An insulation coat 23 is formed on surfaces of the N-type impurity diffusion regions 19 a , 19 b and 19 c .
- a plurality of lowest metal wiring layers 25 a , 25 b and 25 c are separated from each other and formed on the field oxide film and insulation coat 23 .
- the lowest metal wiring layers 25 a , 25 B, 25 c and N-type impurity diffusion regions 19 a , 19 b and 19 c are electrically connected to each other, respectively, through via holes formed through the insulation coat 23 .
- the interlaminar insulation layers 27 are formed on the field oxide film 21 , insulation coat 23 , and lowest metal wiring layers 25 a , 25 b and 25 c . Further, the second metal wiring layers 33 a , 33 b and 33 c each separated from each other, interlaminar insulation layer 35 , the third metal wiring layers 37 a , 37 b and 37 c each separated from each other, interlaminar insulation layer 38 , and the fourth metal wiring layers 39 a , 39 b and 39 c each separated from each other, are laminated in this order on the interlaminar insulation layers 27 . There are formed a plurality of via holes at prescribed locations on the respective interlaminar insulation layers 27 , 35 and 38 .
- the lowest metal wiring layer 25 a , second metal wiring layer 33 a , third metal wiring layer 37 a , and fourth metal wiring layer 39 a are electrically connected to each other.
- the lowest metal wiring layer 25 b , second metal wiring layer 33 b , third metal wiring layer 37 b , and fourth metal wiring layer 39 b are electrically connected to each other.
- the lowest metal wiring layer 25 c , second metal wiring layer 33 c , third metal wiring layer 37 c , and fourth metal wiring layer 39 c are also electrically connected to each other.
- the interlaminar insulation layer 40 is formed on the interlaminar insulation layer 38 and fourth metal wiring layers 39 a , 39 b and 39 c . Further, the I/O cell use Vcc line 13 a , I/O cell use GND line 13 b , each formed from a fifth metal wiring layer, and metal wiring layer 13 c are formed on the interlaminar insulation layer 40 .
- the I/O cell use Vcc line 13 a and I/O cell use GND line 13 b are continuously formed extending over a plurality of pads 7 in a similar manner as shown in the embodiment of FIG. 2B. Referring again to FIG.
- the interlaminar insulation layer 29 is formed on the interlaminar insulation layer 40 and I/O cell use Vcc line 13 a , I/O cell use GND line 13 b and metal wiring layer 13 c .
- a pad area 7 formed from a top metal wiring layer is formed on the interlaminar insulation layer 29 .
- a passivation coat 31 is formed on the interlaminar insulation layer 29 and pad area 7 . The passivation coat 31 forms a pad opening on the pad.
- a coat thickness of each of the lowest metal wiring layers 25 a , 25 b and 25 c , second metal wiring layers 33 a , 33 b and 33 c , third metal wiring layers 37 a , 37 b and 37 c , fourth metal wiring layers 39 a , 39 b and 39 c , I/O cell use Vcc line 13 a , I/O cell use GND line 13 b , metal wiring layer 13 c , and pad area 7 amounts to about 700 nm.
- a coat thickness of each of the metal interlaminar insulation layers 27 , 29 , 35 , 38 and 40 amounts to about 700 nm. Accordingly, the total coat thickness from the surface of the field oxide coat 21 to that of the pad area 7 amounts to about 7700 nm.
- the sixth metal wiring structure can increase a coat thickness in the range right under a pad area 7 in comparison with the three layer metal wiring structure, damage to a semiconductor substrate 3 during bonding can be minimized, and damage of a field transistor forming a protection circuit can substantially be decreased or sometimes prevented.
- the field transistor is utilized for the protection element.
- a MOS transistor having a poly-silicon gate can also be utilized as a protection element of the protection circuit.
- FIGS. 6A, 6B, and 6 C illustrate one embodiment of a protection circuit employing a MOS transistor having a poly-silicon gate as a protection element of a protection circuit.
- the same numeric legends used in FIG. 1 are assigned to portions exerting the same functions in FIGS. 6A and 6B, so that detailed explanation can be omitted.
- FIG. 7 One example of the embodiment of an I/O cell equivalent circuit is illustrated in FIG. 7. The plan view of this embodiment is substantially the same to that of FIG. 2.
- the N-type impurity diffusion regions 19 a , 19 b and 19 c are formed on the surface of the P-type semiconductor substrate 3 being surrounded by a field oxide film 41 .
- the N-type impurity diffusion region 19 a is separated from the N-TYPE IMPURITY diffusion region 19 b .
- the N-type impurity diffusion region 19 b is distanced and located on one side of the N-type impurity diffusion region 19 c , opposite the side of the N-type impurity diffusion region 19 a.
- An insulation coat 43 is formed on the surface of the semiconductor substrate 3 and surfaces of the N-type impurity diffusion regions 19 a , 19 b and 19 c , being surrounded by a field oxide coat 41 .
- a poly-silicon gate 22 a is formed on the insulation coat 43 between the N-type impurity diffusion regions 19 a and 19 b .
- a poly-silicon gate 22 b is also formed on the insulation coat 43 between N-type impurity diffusion regions 19 b and 19 c .
- Another insulation coat is formed on the poly-silicon gates 22 a and 22 b.
- the lowest metal wiring layers 26 a , 26 b and 26 c are formed, being separated from each other, on the insulation coat 43 and poly-silicon gates 22 a and 22 b .
- the lowest metal wiring layer 26 b is formed extending from the poly-silicon gates 22 b to the N-type impurity diffusion region 19 b .
- the lowest metal wiring layer 26 c is formed extending from the poly-silicon gate 22 a to the N-type impurity diffusion region 19 c.
- the lowest metal wiring layer 26 a is electrically connected to the N-type impurity diffusion region 19 a through a via hole formed through the insulation coat 43 .
- the lowest metal wiring layer 26 b is electrically connected to the N-type impurity diffusion region 19 b and poly-silicon gate 22 b through via holes formed in the insulation coat 43 .
- the lowest metal wiring layer 26 c is electrically connected to the N-type impurity diffusion region 19 c and poly-silicon gate 22 a through via holes formed in the insulation coat 43 .
- An interlaminar insulation layer 27 is formed on the field oxide coat 41 , insulation coat 43 , poly-silicon gates 22 a and 22 b , and lowest metal wiring layers 26 a , 26 b , and 26 c . Further, the I/O cell use Vcc line 13 a , I/O cell use GND line 13 b , and metal wiring layer 13 c are formed on the interlaminar insulation layers. The I/O cell use Vcc line 13 a and I/O cell use GND line 13 b are continuously formed extending over a plurality of regions for forming pads 7 as illustrated in FIG. 2B. Referring to FIG.
- the interlaminar insulation layer 29 is formed on the interlaminar insulation layer 27 , I/O cell use Vcc line 13 a , I/O cell use GND line 13 b and metal wiring layer 13 c .
- the lowest metal wiring layers 26 a , 26 b , and 26 c are separately formed from each other on the field oxide coat 41 and insulation coat 43 . Further, the pad area 7 and passivation coat 31 are formed right above the lowest metal wiring layers 26 a , 26 b , and 26 c.
- an input voltage is discharged toward the power supply Vcc or GND by an ON current or punch through current caused by a MOS transistor, which is formed either from the N-type impurity diffusion regions 19 a and 19 c and poly-silicon gate 22 a or that formed from the N-type impurity diffusion regions 19 b and 19 c and poly-silicon gate 22 b.
- FIGS. 8A, 8B and 8 C illustrate another embodiment of a protection circuit employing a field transistor as a protection element.
- the same numeric legends are assigned to portions exerting the same function as that in FIG. 1, and detailed explanation is omitted.
- FIG. 9 illustrates an equivalent circuit of the I/O cell of this embodiment. The plan view of this embodiment is similar to that of the embodiment of FIG. 3.
- the N-type impurity diffusion regions 19 a , 19 b and 19 c are formed on the surface of the P-type semiconductor substrate 3 .
- the field oxide coat 21 separates N-type impurity diffusion regions 19 a , 19 b and 19 c .
- the N-type impurity diffusion region 19 a is formed at a distance from the N-type impurity diffusion region 19 c .
- the N-type impurity diffusion region 19 b is formed at a distance opposite the N-type impurity diffusion region 19 c , and opposite the N-type impurity diffusion region 19 a.
- An insulation coat 23 is formed on the surfaces of the N-type impurity diffusion regions 19 a , 19 b and 19 c .
- the lowest metal wiring layers 45 a , 45 b , and 45 c are separately formed from each other on the insulation coat 23 .
- the lowest metal wiring layers 45 a , 45 b , and 45 c are electrically connected to the N-type impurity diffusion regions 19 a , 19 b , and 19 c , respectively, through via holes formed through the insulation coat 23 .
- the metal wiring layer 45 c is not formed on the field oxide coat 21 .
- An interlaminar insulation layers 27 are formed on a field oxide coat 21 , insulation coat 23 , and lowest metal wiring layers 45 a , 45 b , and 45 c . Further, I/O cell use Vcc line 13 a , I/O cell use GND line 13 b , and metal wiring layer 13 c are formed on the layers 27 . The I/O cell use Vcc line 13 a and GND line 13 b are continuously formed extending over ranges for forming a plurality of pads 7 as illustrated in FIG. 2. Referring again to FIG.
- an interlaminar insulation layer 29 is formed on the interlaminar insulation layer 27 , I/O cell use Vcc line 13 a , I/O cell use GND line 13 b , and metal wiring layer 13 c . Further, the pad area 7 and passivation coat 31 are formed right on the layer 29 .
- respective portions of the N-type impurity diffusion regions 19 a to 19 c are arranged within the range right under die pad area 7 .
- any kind of modifications can be employed as far as a portion or all of the diffusion regions of a protection element of a protection circuit can be arranged right under a pad area 7 and a semiconductor apparatus can be downsized.
- I/O cell use Vcc line 13 a and I/O cell use GND line 13 b serving as power supply lines are formed from metal wiring layers. However, these lines can also be formed from poly-silicon coats made into silicide having a low resistance.
- the equivalent circuit of FIG. 3 includes the input buffer 17 for the I/O cell, the protection circuit and semiconductor apparatus thereof are applicable to an I/O cell equipped with an output buffer instead of the input buffer 17 .
- the protection circuit is formed on a P-type semiconductor substrate
- the protection circuit can also be formed in any one of a P-type well, a N-type semiconductor substrate, and a N-type well.
- a diffusion region may be a P-type. Further, the diffusion region is not limited to a singular layer, and can be multiple.
Abstract
Description
- This application claims priority under 35 USC §119 to Japanese Patent Application No. 2002-090231 filed on Mar. 28, 2002, the entire contents of which are herein incorporated by reference.
- This invention generally relates to a protection circuit for preventing destruction of an internal circuit possibly caused by excessive voltage input from a pad, and to a semiconductor apparatus employing the protection circuit.
- While there have been some attempts to protect internal circuits from destruction, these attempts have not been entirely successful.
- FIGS. 10A and 10B entirely and partially illustrate GND (ground) and power supply pads mounted on a
conventional semiconductor apparatus 46 formed from a P-type semiconductor substrate 3. As shown in FIG. 10A, aninner core region 5 is formed at a central portion of thesemiconductor apparatus 46. An inner circuit formed from a plurality of semiconductor elements is located in theinner core region 5. A plurality ofpad areas 7 is also formed in anouter region 15 of thesemiconductor apparatus 46. An I/O cell 47 is provided perpad area 7 on thesemiconductor substrate 3 between theinner core region 5 andpad area 7. There are provided an inner core region useVcc line 11 a and an inner core region use GND (ground)line 11 b, each formed from a metal wiring layer, between theinner core region 5 and I/O cell 47.Lines inner core region 5. Further, to continuously extend over a plurality of I/O cells 47, an I/O celluse Vcc line 49 a and an I/O cell useGND line 49 b, each formed from a metal wiring layer, are provided. - As shown in FIG. 10B, the inner core region use
Vcc line 11 a and I/O celluse Vcc line 49 a are electrically connected to ametal wiring layer 51 a which is electrically connected to an electric power supplyuse pad area 7 a through viaholes GND line 11 b and I/O cell useGND line 49 b are electrically connected to themetal wiring layer 51 b which is electrically connected to a GNDuse pad area 7 b through viaholes Vcc line 11 a is electrically connected to ametal wiring layer 53 a extending over in the side ofinner core region 5 through avia hole 11 e. The inner core region useGND line 11 b is electrically connected to ametal wiring layer 53 b extending over to the side ofinner core region 5 through avia hole 11 f. - FIG. 11 illustrates an exemplary configuration of a
conventional pad area 7 and I/O cell 47. FIG. 12 illustrates an equivalent circuit thereof. Each I/O cell 47 is configured from a protection circuit andinput buffer 17. The protection circuit is configured from a P-channel type MOSFET (Metal Oxide Silicon Field Effect Transistor) Tr5 (herein after referred to as a MOS transistor Tr5), a N-channel type MOS transistor Tr6, and a resister R (not shown). - As shown in FIG. 11, the MOSFET transistor Tr5 is formed in a P channel region of a N-well formed on the P-type semiconductor substrate. A gate electrode is configured from a
polysilicon electrode 55. An area required for forming the MOS transistor Tr5 is approximately 1800 μm. The MOS transistor Tr6 is formed in an N-channel region of a P-type semiconductor substrate. Both source and drain of the MOS transistor Tr6 are configured from a N-type impurity diffusion layer (N-type impurity) formed on the P-type semiconductor substrate. A gate electrode is configured from apolysilicon electrode 57. An area required for forming the MOS transistor Tr6 is approximately 1000 μm. - As depicted in FIG. 12, both the poly-
silicon gate electrode 55 and a source of the MOS transistor Tr5 are connected to power supply “Vcc”. Respective drains of the MOS transistors Tr5 and Tr6 are connected to each other, and further connected to thepad area 7. Both the poly-silicon gate electrode 57 and source of the MOS transistor Tr6 are connected to ground “GND”. One end of the resistance is connected to a connection point connecting drains of the MOS transistors Tr5 and Tr6. - As further shown in FIGS. 11 and 12, the
input buffer 17 is configured from an inverter circuit formed from P-channel type and N-channel type MOS transistors Tr3 and Tr4. The MOS transistor Tr3 is formed in the P-channel region of the N-well formed on the P-type semiconductor substrate. Both the source and drain of the MOS transistor Tr3 are configured from P-type impurity diffusion layers formed in the N-well. A gate electrode is configured from apolysilicon electrode 59. The MOS transistor Tr4 is formed in an N-channel region of the P-type semiconductor substrate. Both the source and drain of the MOS transistor Tr4 are configured from N-type impurity diffusion layers (N-type impurity) formed on a P-type semiconductor substrate. A gate electrode is configured from apolysilicon electrode 61, as shown in FIG. 11. - As depicted in FIG. 12, the source of the MOS transistor Tr3 is connected to the power supply “Vcc”. The source of the MOS transistor Tr4 is connected to ground (GND). Respective drains of the MOS transistors Tr3 and Tr4 are connected to each other, and are lead to the
inner core region 5.Respective polysilicon gates - As illustrated in FIGS.10 to 12, none of the circuits are conventionally formed on the
pad area 7 of thesemiconductor substrate 3. That is, punching through phenomenon occurs in a metal wiring layer forming thepad area 7 when wire-bonding is performed with a bonding wire so as to electrically connect thepad area 7 to an external terminal during an assembling process for the semiconductor apparatus. As a countermeasure, a well or the like is formed in the range of thepad area 7 on thesemiconductor substrate 3. - Further, based upon recent miniaturization, downsizing (i.e., shrinkage) is promoted in order to decrease cost for a semiconductor product. For the purpose of avoiding destruction of an internal circuit caused by a voltage excessively input from a pad, a protection circuit for an I/O cell is typically provided.
- However, since a withstand pressure of a MOS transistor simply decreases in accordance with the miniaturization, and an area occupied by the protection circuit cannot be minimized, the protection circuit prevents the shrinkage.
- Further, in accordance with the miniaturization, the inner core region is downsized, and accordingly, the I/O cell increases a rate of its occupation in a semiconductor apparatus. Thus, when shrinkage is promoted, there are pressing needs to minimize the area occupied by the I/O cell in the semiconductor apparatus. Further, as illustrated in FIG. 11, a rate of an area for a
pad area 7 is high. - However, since multiple layers, formed from inter-laminar insulation layers and metal wiring layers, are formed between a surface of a pad and a semiconductor substrate by a recent multiple layer technology of metal wiring layers, damage to the semiconductor substrate, caused by the wire bonding in the pad area, does not prominently occur in comparison with that in the past. In addition, even formation of a well is needless nowadays. Despite that, semiconductor apparatus used in the past generally are configured to form none of the semiconductor elements within a pad area.
- As a conventional technology that efficiently utilizes a pad area, Japanese patent application Laid Open No. 2000-12778 discloses one example. Specifically, a protection circuit is formed on an N-type semiconductor substrate, having an NPN configuration. The protection circuit is formed from an N-implant diffusion layer, a P-type island region including a P-implant layer and P-diffusion layer, and a N-diffusion layer formed on the island region.
- However, when the protection circuit, disclosed in Japanese patent application Laid Open No. 2000-12778, is formed, both N and P-type implant layers are necessitated. As a result, a problem of increasing a number of manufacturing processes occurs when such a manner is applied to a semiconductor apparatus excluding an implant layer.
- Accordingly, an object of the present invention is to address such problems and provide a new protection circuit for use in a semiconductor apparatus. The protection circuit includes a first conductivity type semiconductor substrate, a second conductivity type first diffusion region formed on the semiconductor substrate, and a second conductivity type second diffusion region formed on the semiconductor substrate. The second diffusion region is distanced at a prescribed interval from the first diffusion region, and the first diffusion region is electrically connected to a pad for electrically connecting the inner circuit to an outside region. The second diffusion region is electrically connected to a power supply. At least a portion of said first and second diffusion regions is formed right under a pad area.
- In another embodiment, the first and second diffusion regions are substantially entirely formed right under the pad area.
- In another embodiment, the first and second diffusion regions are separated from each other by a field oxide coat formed on the surface of the semiconductor substrate. At least a portion of the field oxide coat is located right under the pad area.
- In yet another embodiment, a second conductivity type third diffusion region is formed on the surface of the semiconductor substrate and located in an opposite side at a prescribed interval from the first diffusion region to the second diffusion region. The second diffusion region is electrically connected to a higher voltage of the power supply. The third diffusion region is electrically connected to a lower voltage of the power supply. At least a portion of the third diffusion region is formed right under the pad area.
- In still another embodiment, the third diffusion region is substantially entirely formed right under the pad area.
- In yet another embodiment, the first and second diffusion regions, and the first and third diffusion regions are separated, respectively, from each other by a field oxide coat. At least a portion of the pad area is formed on the field oxide coat.
- In yet another embodiment, the electrical connection is performed by at least one via hole formed right under the pad area.
- A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
- FIG. 1A is a chart when viewed from a section C-C illustrated in FIGS. 1B and 1C;
- FIG. 1B is a chart when viewed from a section A-A illustrated in FIG. 1A;
- FIG. 1C is a chart when viewed from a section B-B illustrated in FIG. 1A;
- FIG. 2A is a plan view illustrating one embodiment;
- FIG. 2B is an enlarged view illustrating a portion framed by a circle (dotted circle) in FIG. 2A;
- FIG. 3 is a chart illustrating one example of an equivalent circuit of a
pad area 7 and I/O cell 9; - FIG. 4A is a cross-sectional view illustrating one example of an outer region of a Vcc use pad;
- FIG. 4B is a cross-sectional view illustrating one example of an outer region of a GND use pad;
- FIG. 5 is a cross-sectional view illustrating an exemplary protection circuit applied to a six-layer metal wiring structure;
- FIG. 6A is a cross-sectional view illustrating one example of an outer region of a protection circuit employing a MOS transistor having a poly-silicon gate as a protection element;
- FIG. 6B is a chart when viewed from a section A-A of FIG. 6A;
- FIG. 6C is a chart when viewed from a section B-B of FIG. 6A;
- FIG. 7 is a chart illustrating one example of an equivalent circuit of a pad and I/O cell;
- FIG. 8A is a chart illustrating another embodiment of a protection circuit employing a field transistor as a protection element, when viewed from a section CC of FIGS. 8B and 8C;
- FIG. 8B is a plan view when viewed from a section A-A of FIG. 8A;
- FIG. 8C is a chart when viewed from a section B-B of FIG. 8A;
- FIG. 9 is a chart illustrating another example of an equivalent circuit of an I/O cell;
- FIG. 10A is a plan view entirely illustrating a conventional semiconductor apparatus;
- FIG. 10B is an enlarged plan view partially illustrating GND and a pad;
- FIG. 11 is a plan view illustrating an example of a
pad area 7 and I/O cell 47; - FIG. 12 is a chart illustrating an equivalent circuit of the conventional pad and I/O cell; and
- FIG. 13 is a chart showing an example of a table showing surge impressed voltages and conditions of energy divergence factors.
- Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout several views, in particular, in FIGS. 1A, 1B,2A and 2B, one embodiment of an outer region of a protection circuit of a semiconductor apparatus is illustrated.
- As depicted in FIG. 2A, an
inner core region 5 is formed at a central section of asemiconductor apparatus 1 formed from a P-type semiconductor substrate 3. An inner circuit formed from a plurality of semiconductor elements is formed in theinner core region 5. A plurality of pads is also formed in an outer region of thesemiconductor apparatus 1. Referring to FIG. 2B, an I/O cell 9 is arranged per apad area 7 on thesemiconductor substrate 3, including a range for forming thepad area 7. An inner core region useVcc line 11 a and an inner core region useGND line 11 b, each formed from a metal wiring layer, are continuously formed between theinner core region 5 and I/O cell 9 almost surrounding theinner core region 5. An I/O cell useVcc line 13 a and an I/O celluse GND line 13 b, each formed from a metal wiring layer, are continuously formed, extending over regions for forming a plurality of pads. Such a Vcc represents a high potential of a power supply. The GND represents a lower potential of the power supply. - The inner core region use
Vcc line 11 a and I/O cell useVcc line 13 a are configured by metal wirings arranged on a layer lower than thepad area 7. The inner core region useVcc line 11 a and I/O cell useVcc line 13 a are electrically connected to a power supplyuse pad area 7 via a metal wiring layer (not shown) formed on a layer where thepad area 7 is formed. The inner core region useGND line 11 b and I/O celluse GND line 13 b are configured by metal wirings arranged on a layer lower than thepad area 7. The inner core region useGND line 11 b and I/O celluse GND line 13 b are electrically connected to a GNDuse pad area 7 via the metal wiring layer (not shown) formed on the layer where thepad area 7 is formed. - FIG. 3 illustrates one example of an equivalent circuit of a
pad area 7 and I/O cell 9. Aprotection circuit 15 and aninput buffer 17 configure each I/O cell 9. Theprotection circuit 15 is configured from an N-channel type field transistor Tr1, a N-channel type field transistor Tr2, and a resistance R formed from a diffusion layer. Even though the diffusion layer configures the resistance R, a resistance formed from a polysilicon coat and a metal lamina can be utilized therefor. - As illustrated in FIG. 3, the drain of the N-channel type field transistor Tr1 is connected to the power supply Vcc. The source and drain of the field transistors Tr1 and Tr2, respectively, are connected to each other, and then connected to the
pad area 7. The gate electrodes of the field transistors Tr1 and Tr2 are connected to each other, and then connected to thepad area 7. One end of the resistance R is connected to a connection point connecting the source of the field transistor Tr1 to the drain of the field transistor Tr2. - As further shown in FIG. 3, an inverter circuit formed from P-channel type and N-channel type MOS transistors Tr3 and Tr4 configures the
input buffer 17. The source of the MOS transistor Tr3 is connected to the power source Vcc. The source of the MOS transistor Tr4 is connected to GND. The drains of the MOS transistors Tr3 and Tr4, respectively, are connected to each other, and then lead to theinner core region 5. The gate electrodes of the MOS transistors Tr3 and Tr4, respectively, are connected to each other, and then connected to the other end of the resistance R. - Although illustrations of the diffusion type resistance R and MOS transistors Tr3 and Tr4 are omitted, the diffusion type resistance R is formed on a P-
type semiconductor substrate 3 between thepad area 7 in an I/O cell 9 formation region and the inner core region useVcc line 11 a. - Referring to FIG. 1A, a configuration of the
protection circuit 15 is described other than the resistance R. Plural N-typeimpurity diffusion regions oxide film 21 separates these N-typeimpurity diffusion regions impurity diffusion region 19 a is distanced from the N-typeimpurity diffusion region 19 c. The N-typeimpurity diffusion region 19 b is formed in an opposite side and distanced from the N-typeimpurity diffusion region 19 c and the N-typeimpurity diffusion region 19 a. The N-typeimpurity diffusion region 19 a constitutes a second diffusion range forming the protection circuit of the semiconductor apparatus. The N-typeimpurity diffusion region 19 b serves as a third diffusion region. The N-typeimpurity diffusion region 19 c serves as a first diffusion region. - The N-type
impurity diffusion region 19 a corresponds to the drain of the field transistor Tr1 of FIG. 3. The N-typeimpurity diffusion region 19 b corresponds to the source of the field transistor Tr2 of FIG. 3. The N-typeimpurity diffusion region 19 c corresponds to the source of the field transistor Tr1 and the drain of the field transistor Tr2 of FIG. 3. - An
insulation coat 23 is formed on the surfaces of the N-typeimpurity diffusion regions field oxide coat 21 andinsulation coat 23. The lowestmetal wiring layer 25 a is also electrically connected to the N-typeimpurity diffusion region 19 a through a via hole formed through theinsulation coat 23. The lowestmetal wiring layer 25 b is electrically connected to the N-typeimpurity diffusion region 19 b through a via hole formed through theinsulation coat 23. The lowestmetal wiring layer 25 c is electrically connected to the N-typeimpurity diffusion region 19 c through a via hole formed in theinsulation coat 23. The lowestmetal wiring layer 25 c is formed on thefield oxide coat 21 extending over from a portion between the N-typeimpurity diffusion regions impurity diffusion regions metal wiring layer 25 c corresponds to the gate electrodes of the field transistors Tr1 and Tr2 of FIG. 3. - An
interlaminar insulation layer 27 is formed on thefield oxide coat 21,insulation coat 23, and lowest metal wiring layers 25 a, 25 b, and 25 c. Further, an I/O cell useVcc line 13 a, an I/O celluse GND line 13 b, and ametal wiring layer 13 c each formed from a metal wiring layer are formed on the layers. The I/O cell useVcc line 13 a, and I/O celluse GND line 13 b are continuously formed extending over a region, where a plurality of pads are formed thereabove, as illustrated in FIG. 2B. - As shown in FIG. 1A, there are provided via holes through the
interlaminar insulation layer 27 for electrically connecting the lowest metal wiring layers 25 a, 25 b, and 25 c to I/O cell useVcc lines metal wiring layer 25 b to I/O celluse GND line 13 b, and the lowestmetal wiring layer 25 c tometal wiring layer 13 c, respectively. - Also illustrated in FIG. 1A, an
inter-laminar insulation layer 29 is formed on theinter-laminar insulation layer 27, I/O cell useVcc line 13 a, I/O celluse GND line 13 b, andmetal wiring layer 13 c. Further, apad area 7, formed from a metal wiring layer, is formed on the layers. Apassivation coat 31 is formed on theinter-laminar insulation layer 29 andpad area 7. There is formed a pad opening section on apad area 7 of thepassivation coat 31. A plurality of via holes are formed so as to electrically connect themetal wiring layer 13 c to thepad area 7. - As illustrated in FIG. 4A, any one of
pads 7 on thesemiconductor apparatus 1 is utilized as a Vccuse pad area 7 a. A plurality of via holes are formed through theinter-laminar insulation coat 29 right under a Vccuse pad area 7 a so as to electrically connect the Vccuse pad area 7 a to the I/O cell useVcc line 13 a. - Further, as shown in FIG. 4B, any one of
pads 7 on thesemiconductor apparatus 1 beside the Vccuse pad area 7 a, is utilized as a GNDuse pad area 7 b. A plurality of via holes are formed through theinter-laminar insulation coat 29 right under a GNDuse pad area 7 b so as to electrically connect the GNDuse pad area 7 b to the I/O celluse GND line 13 b. - One example of an operation of the
protection circuit 15 is now described with reference to FIGS. 3 and 13. - As listed in Table 1 of FIG. 13, a surge-impressed voltage represents a voltage excessively impressed to a
pad area 7. In general, a surge test is executed by a method, called HBM (Human Body Model), and various impressed voltages shown in the Table 1 are utilized. - When +2 kv (kilo volt) is impressed to the
pad area 7 relative to the power supply Vcc, the field transistor Tr1 is turned ON. Then, such a surge-impressed voltage is decreased to the power supply Vcc level due to discharge, i.e., an ON current. When −2 kv is impressed to thepad area 7 relative to the power supply Vcc, a punch through current flows through the field transistor Tr1, and the surge-impressed voltage is increased to the power supply Vcc (as shown in column (1) of Table 1). - When +2 kv is impressed to the
pad area 7 relative to the GND, the field transistor Tr2 is turned ON, and the surge impressed voltage is decreased to a GND level due to discharge, i.e., an ON current (shown in column (3) of Table 1). When −2 kv is impressed to thepad area 7 relative to GND, a punch through current flows through the field transistor Tr2, and the surge impressed voltage increases to the GND level (as shown in column (2) of Table 1). In this way, even if an input voltage is excessively impressed to thepad area 7, both MOS transistors Tr3 and Tr4, forming aninput buffer 17, can be protected. - Thus, since the field transistors Tr1 and Tr2 collectively constituting the
protection circuit 15 are formed right under thepad area 7, an area for asemiconductor apparatus 1 can be downsized. Further, since the I/O cell useVcc line 13 a and an I/O celluse GND line 13 b are also formed right under thepad area 7, an area for asemiconductor apparatus 1 can be downsized. - Further, since damage to the
pad area 7 by wire bonding during an assembling process is not completely negligible, a change in property caused by the damage is also not negligible when a semiconductor element is arranged right under the pad area. Accordingly, a semiconductor element designed by simulating based upon a basic property cannot be arranged there. However, since the protection circuit is not generally simulated and is enough if functional, delicate designing is not generally required. Accordingly, the field transistors Tr1 and Tr2 forming theprotection circuit 15 raise no problem even if formed right under thepad area 7. - As described heretofore, this embodiment employs the three layer metal wiring structure as illustrated in FIG. 1A. However, one, two, and more than four layer metal wiring structures can be employed in a semiconductor apparatus. In addition, when the one layer metal wiring structure is employed, both the power supply and GND lines are formed other than the range for the pad.
- When a design rule is about a half micron, the three layer metal wiring shown in FIG. 1A has been prevailing. A thickness of each of the lowest metal layer wiring layers25 a, 25 b and 25 c, I/O cell use
Vcc line 13 a, I/O celluse GND line 13 b,metal wiring layer 13 c, andpad area 7 amount to almost 700 nm (nanometer), and that of the interlaminar insulation layers 27 and 29 almost 800 nm, respectively. Accordingly, a coat thickness from the surface of the field oxide film to that of thepad area 7 amounts to about 3700 nm in the three metal wiring structures. - Further, the design rule includes dimensions that are quarter or sub-quarter micron. The six-layer metal wiring structure that employs such a design rule may be employed in the semiconductor apparatus.
- FIG. 5 is a cross-sectional view illustrating an exemplary protection circuit employing the six layer metal wiring structure. By assigning the same numeric legends to sections functioning in a manner similar to those in FIG. 1, detailed descriptions are omitted. The N-type
impurity diffusion regions field oxide film 2 and formed on the surface of the P-type semiconductor substrate 3. Aninsulation coat 23 is formed on surfaces of the N-typeimpurity diffusion regions insulation coat 23. The lowest metal wiring layers 25 a, 25B, 25 c and N-typeimpurity diffusion regions insulation coat 23. - The interlaminar insulation layers27 are formed on the
field oxide film 21,insulation coat 23, and lowest metal wiring layers 25 a, 25 b and 25 c. Further, the second metal wiring layers 33 a, 33 b and 33 c each separated from each other,interlaminar insulation layer 35, the third metal wiring layers 37 a, 37 b and 37 c each separated from each other,interlaminar insulation layer 38, and the fourth metal wiring layers 39 a, 39 b and 39 c each separated from each other, are laminated in this order on the interlaminar insulation layers 27. There are formed a plurality of via holes at prescribed locations on the respective interlaminar insulation layers 27, 35 and 38. The lowestmetal wiring layer 25 a, secondmetal wiring layer 33 a, thirdmetal wiring layer 37 a, and fourthmetal wiring layer 39 a are electrically connected to each other. In addition, the lowestmetal wiring layer 25 b, secondmetal wiring layer 33 b, thirdmetal wiring layer 37 b, and fourthmetal wiring layer 39 b are electrically connected to each other. The lowestmetal wiring layer 25 c, secondmetal wiring layer 33 c, thirdmetal wiring layer 37 c, and fourthmetal wiring layer 39 c are also electrically connected to each other. - As illustrated in FIG. 5, the
interlaminar insulation layer 40 is formed on theinterlaminar insulation layer 38 and fourth metal wiring layers 39 a, 39 b and 39 c. Further, the I/O cell useVcc line 13 a, I/O celluse GND line 13 b, each formed from a fifth metal wiring layer, andmetal wiring layer 13 c are formed on theinterlaminar insulation layer 40. The I/O cell useVcc line 13 a and I/O celluse GND line 13 b are continuously formed extending over a plurality ofpads 7 in a similar manner as shown in the embodiment of FIG. 2B. Referring again to FIG. 5, theinterlaminar insulation layer 29 is formed on theinterlaminar insulation layer 40 and I/O cell useVcc line 13 a, I/O celluse GND line 13 b andmetal wiring layer 13 c. Apad area 7 formed from a top metal wiring layer is formed on theinterlaminar insulation layer 29. Apassivation coat 31 is formed on theinterlaminar insulation layer 29 andpad area 7. Thepassivation coat 31 forms a pad opening on the pad. - A coat thickness of each of the lowest metal wiring layers25 a, 25 b and 25 c, second metal wiring layers 33 a, 33 b and 33 c, third metal wiring layers 37 a, 37 b and 37 c, fourth metal wiring layers 39 a, 39 b and 39 c, I/O cell use
Vcc line 13 a, I/O celluse GND line 13 b,metal wiring layer 13 c, andpad area 7 amounts to about 700 nm. A coat thickness of each of the metal interlaminar insulation layers 27, 29, 35, 38 and 40 amounts to about 700 nm. Accordingly, the total coat thickness from the surface of thefield oxide coat 21 to that of thepad area 7 amounts to about 7700 nm. - Thus, since the sixth metal wiring structure can increase a coat thickness in the range right under a
pad area 7 in comparison with the three layer metal wiring structure, damage to asemiconductor substrate 3 during bonding can be minimized, and damage of a field transistor forming a protection circuit can substantially be decreased or sometimes prevented. - According to the above-described embodiment, the field transistor is utilized for the protection element. However, a MOS transistor having a poly-silicon gate can also be utilized as a protection element of the protection circuit.
- FIGS. 6A, 6B, and6C illustrate one embodiment of a protection circuit employing a MOS transistor having a poly-silicon gate as a protection element of a protection circuit. The same numeric legends used in FIG. 1 are assigned to portions exerting the same functions in FIGS. 6A and 6B, so that detailed explanation can be omitted. One example of the embodiment of an I/O cell equivalent circuit is illustrated in FIG. 7. The plan view of this embodiment is substantially the same to that of FIG. 2.
- Referring to FIG. 6A, the N-type
impurity diffusion regions type semiconductor substrate 3 being surrounded by afield oxide film 41. The N-typeimpurity diffusion region 19 a is separated from the N-TYPEIMPURITY diffusion region 19 b. The N-typeimpurity diffusion region 19 b is distanced and located on one side of the N-typeimpurity diffusion region 19 c, opposite the side of the N-typeimpurity diffusion region 19 a. - An
insulation coat 43 is formed on the surface of thesemiconductor substrate 3 and surfaces of the N-typeimpurity diffusion regions field oxide coat 41. A poly-silicon gate 22 a is formed on theinsulation coat 43 between the N-typeimpurity diffusion regions silicon gate 22 b is also formed on theinsulation coat 43 between N-typeimpurity diffusion regions silicon gates - The lowest metal wiring layers26 a, 26 b and 26 c are formed, being separated from each other, on the
insulation coat 43 and poly-silicon gates metal wiring layer 26 b is formed extending from the poly-silicon gates 22 b to the N-typeimpurity diffusion region 19 b. The lowestmetal wiring layer 26 c is formed extending from the poly-silicon gate 22 a to the N-typeimpurity diffusion region 19 c. - The lowest
metal wiring layer 26 a is electrically connected to the N-typeimpurity diffusion region 19 a through a via hole formed through theinsulation coat 43. The lowestmetal wiring layer 26 b is electrically connected to the N-typeimpurity diffusion region 19 b and poly-silicon gate 22 b through via holes formed in theinsulation coat 43. In addition, the lowestmetal wiring layer 26 c is electrically connected to the N-typeimpurity diffusion region 19 c and poly-silicon gate 22 a through via holes formed in theinsulation coat 43. - An
interlaminar insulation layer 27 is formed on thefield oxide coat 41,insulation coat 43, poly-silicon gates Vcc line 13 a, I/O celluse GND line 13 b, andmetal wiring layer 13 c are formed on the interlaminar insulation layers. The I/O cell useVcc line 13 a and I/O celluse GND line 13 b are continuously formed extending over a plurality of regions for formingpads 7 as illustrated in FIG. 2B. Referring to FIG. 6A, theinterlaminar insulation layer 29 is formed on theinterlaminar insulation layer 27, I/O cell useVcc line 13 a, I/O celluse GND line 13 b andmetal wiring layer 13 c. The lowest metal wiring layers 26 a, 26 b, and 26 c are separately formed from each other on thefield oxide coat 41 andinsulation coat 43. Further, thepad area 7 andpassivation coat 31 are formed right above the lowest metal wiring layers 26 a, 26 b, and 26 c. - When excessively impressed to the
pad area 7, an input voltage is discharged toward the power supply Vcc or GND by an ON current or punch through current caused by a MOS transistor, which is formed either from the N-typeimpurity diffusion regions silicon gate 22 a or that formed from the N-typeimpurity diffusion regions silicon gate 22 b. - FIGS. 8A, 8B and8C illustrate another embodiment of a protection circuit employing a field transistor as a protection element. The same numeric legends are assigned to portions exerting the same function as that in FIG. 1, and detailed explanation is omitted. FIG. 9 illustrates an equivalent circuit of the I/O cell of this embodiment. The plan view of this embodiment is similar to that of the embodiment of FIG. 3.
- Referring to FIG. 8A, the N-type
impurity diffusion regions type semiconductor substrate 3. Thefield oxide coat 21 separates N-typeimpurity diffusion regions impurity diffusion region 19 a is formed at a distance from the N-typeimpurity diffusion region 19 c. The N-typeimpurity diffusion region 19 b is formed at a distance opposite the N-typeimpurity diffusion region 19 c, and opposite the N-typeimpurity diffusion region 19 a. - An
insulation coat 23 is formed on the surfaces of the N-typeimpurity diffusion regions insulation coat 23. The lowest metal wiring layers 45 a, 45 b, and 45 c are electrically connected to the N-typeimpurity diffusion regions insulation coat 23. Themetal wiring layer 45 c is not formed on thefield oxide coat 21. - An interlaminar insulation layers27 are formed on a
field oxide coat 21,insulation coat 23, and lowest metal wiring layers 45 a, 45 b, and 45 c. Further, I/O cell useVcc line 13 a, I/O celluse GND line 13 b, andmetal wiring layer 13 c are formed on thelayers 27. The I/O cell useVcc line 13 a andGND line 13 b are continuously formed extending over ranges for forming a plurality ofpads 7 as illustrated in FIG. 2. Referring again to FIG. 8A, aninterlaminar insulation layer 29 is formed on theinterlaminar insulation layer 27, I/O cell useVcc line 13 a, I/O celluse GND line 13 b, andmetal wiring layer 13 c. Further, thepad area 7 andpassivation coat 31 are formed right on thelayer 29. - When a voltage is excessively input and impressed toward the
pad area 7, the voltage is discharged by the power supply Vcc or GND by a punch through current of a field transistor formed either from the P-type semiconductor substrate and N-typeimpurity diffusion regions impurity diffusion regions - According to the above-described embodiments shown in FIGS.1 to 9, respective of the N-type
impurity diffusion regions pad area 7 are included. However, the first to third diffusion regions can be entirely formed right under the range of thepad area 7. - Further, respective portions of the N-type
impurity diffusion regions 19 a to 19 c are arranged within the range right underdie pad area 7. However, any kind of modifications can be employed as far as a portion or all of the diffusion regions of a protection element of a protection circuit can be arranged right under apad area 7 and a semiconductor apparatus can be downsized. - Further, I/O cell use
Vcc line 13 a and I/O celluse GND line 13 b serving as power supply lines are formed from metal wiring layers. However, these lines can also be formed from poly-silicon coats made into silicide having a low resistance. - Still further, even though the equivalent circuit of FIG. 3 includes the
input buffer 17 for the I/O cell, the protection circuit and semiconductor apparatus thereof are applicable to an I/O cell equipped with an output buffer instead of theinput buffer 17. - Further, even though, in at least one embodiment, the protection circuit is formed on a P-type semiconductor substrate, the protection circuit can also be formed in any one of a P-type well, a N-type semiconductor substrate, and a N-type well. When the protection circuit is formed on the N-type semiconductor substrate or N-type well, a diffusion region may be a P-type. Further, the diffusion region is not limited to a singular layer, and can be multiple.
- Numerous additional modifications and variations of the present invention are possible in light of the above teachings. Accordingly, the invention is not to be considered as being limited by the foregoing description and drawings, but is only limited by the scope of the appended claims.
Claims (25)
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JP2002090231A JP2003289104A (en) | 2002-03-28 | 2002-03-28 | Protection circuit for semiconductor device and the semiconductor device |
JP2002-090231 | 2002-03-28 |
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US20030223164A1 true US20030223164A1 (en) | 2003-12-04 |
US6858885B2 US6858885B2 (en) | 2005-02-22 |
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